You don't need to specify the holes on Housing Profile 2. This is where you want to use our square nuts (GGSO9903). They slide right into Housing Profile 2. You can move them to the desired position and line them up with the cover panel.

You are right, there is no equation for placing a bracket on the slotted side of Housing Profile 2.
The distances for placing the bracket holes depend on your material thickness and if you keep the 2mm recommended remaining material to cover the slot. I can double check your design if you like, just email me your fpd files.